Display probability modulates attentional capture by onset distractors.

Attention can be stimulus-driven and bottom-up or goal-driven and top-down. Bottom-up attention and, particularly, attentional capture are often thought to be strongly automatic, i.e., not modulable. For example, in visual search, it has been shown that salient distractors strongly attract attention even though observers were instructed to ignore them. However, it was also shown that the strength of distraction can be modulated by the display probabilities of the distractors. Hence, bottom-up attention seems not to be completely automatic. In these studies, the distractors were salient by color differences to the other items in the display. Such color distractors, however, do not necessarily trigger bottom-up attention. Here, we presented onset distractors, that is, distractors displayed after the onset of the other search items, which are thought to strongly elicit bottom-up attention and to capture eye movements. Varying the display probabilities of the onset distractors strongly modulated attentional capture. We suggest that modulation was due to statistical learning. This study adds further evidence that bottom-up processes are not completely automatic.